Caffeinated Curiosity ~ Part Two: Endurance Awesomeness
I AM WRITING THIS POST AT 6am UK TIME WITH AN AWESOME MIX OF JET LAG AND CAFFEINE AND I AM SO AWAKE!
First of all, lets address some basic temperature issues. Since when did it become ok to call it mild? It is not MILD, it is cold. End #ThailandProblems
Anyway… Now that we all understand how caffeine affects our physiology – lets get nerdy with how that can positively impact our performance.
Caffeine for Endurance Performance
Various studies to date have shown that caffeine ingested prior to (Graham & Spriet, 1995; Ganio et al, 2009) and during (Cox et al, 2002) prolonged sub-maximal and highâ€¨intensity exercise can improve endurance performance. Since the early work of Costill and colleagues (1978) it has often been cited that caffeine induces its ergogenic effects by an increase in fat oxidation throughâ€¨ the sympathetic nervous system, and a sequential sparing of muscle glycogen (Spriet et al, 1992). However, there is very little support for an increase in fat oxidation rates (Chesley et al, 1998; Graham & Spriet) or enhancement of the sympathetic nervous system (Mohr et al, 1998) being the principal mechanism ofâ€¨ caffeineâ€™s ergogenic effect.
Recent research has elucidated that the principal mechanism of caffeine’s ergogenic effects is through its ability to act as an adenosine receptor antagonist (as outlined in part one) to induce effects on both central and peripheral nervous systems (Tarnopolsky, 2008) to reduce pain and exertion perception (Doherty & Smith, 2005), improve motor recruitment (Tarnopolsky, 2008) and excitation-contraction coupling (Mohr et al, 2011; Tarnopolsky & Cupido, 2000). Caffeine has been shown to increase serotonin concentrations in the regions of the brain that have excitatory projections to spinal motor neurons, which increases the self-sustained firing of the skeletal muscle motor units that are enervated by these neurons (Walton et al, 2002).
A motor unit consists of a motor neuron and the skeletal muscle fibres that are innervated by that motor neuron’s axonal terminals. Groups of motor units often work together to coordinate the contractions of a single muscle. All muscle fibres in a motor unit are of the same fibre type and contract when a motor unit is activated.
Caffeine = > Motor Unit Recruitment = > Enhanced Muscular Contraction
Caffeine’s ability to enhance the sensitivity of these motor units has been shown to postpone fatigue and increase endurance performance (Walton et al, 2002). In the literature to date, the ergogenic effects of caffeine are well documented with the time to exhaustion test at a fixed power output being the predominant performance measure used (Graham & Spriet, 1995; Spriet et al, 1992; Costill et al, 1978; Graham & Spriet, 1991). It has been questioned whether assessing endurance capacity in this way would have sufficient validity to translate results to real life events (Wiles et al, 1992). However since then, a number of studies have confirmed the ergogenic effects of caffeine using time trial protocols (Jenkins et al, 2000; Desbrow et al, 2012; Ganio et al, 2009).
A time trial protocol involves completing energy based targets or set distances in as fast a time as possible, thus simulating variable intensities that are likely to occur during competitive events.
It is pretty evident that caffeine rocks and is great for all you endurance nuts! But how do you get your caffeine intake? Coffee right? As the above studies tend to administer caffeine before exercise either diluted in water or in pill form, it is important to distinguish if there is a differential effect between this supplementation and drinking coffee?
Keep your eyes peeled for next weeks’ final post in this three part series where we analyse the difference between coffee and caffeine!
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Walton C, Kalmar JM, Cafarelli E. Effect of caffeine on self-sustained firing in human motor units. J Physiol 2002;545:6719.
Graham TE, Spriet LL (1995) Metabolic, catecholamine, and exercise performance responses to various doses of caffeine. J Appl Physiol 78: 867-74.
Ganio MS, Klau JF, Casa DJ, Armstrong LE, Maresh CM (2009) Effect of caffeine on sport-specific endurance performance: a systematic review. J Strength Cond Res 23: 315-324.
Costill DL, Dalsky GP, Fink WJ (1978) Effects of caffeine ingestion on metabolism and exercise performance. Med Sci Sports 10: 155-158.
Spriet LL, MacLean DA, Dyck DJ, Hultman E, Cederblad G, et al. (1992) Caffeine ingestion and muscle metabolism during prolonged exercise in humans. Am J Physiol 262: E891-E898.
Chesley A, Howlett RA, Heigenhauser GJ, Hultman E, Spriet LL (1998) Regulation of muscle glycogenolytic flux during intense aerobic exercise after caffeine ingestion. Am J Physiol 275: R596-603.
Graham TE, Spriet LL (1991) Performance and metabolic responses to a high â€¨caffeine dose during prolonged exercise. J Appl Physiol 71: 2292-2298.
Mohr T, Van Soeren M, Graham TE, Kjaer M (1998) Caffeine ingestion and metabolic responses of tetraplegic humans during electrical cycling. Journal of applied physiology 85: 979-985.
Tarnopolsky MA (2008) Effect of caffeine on the neuromuscular system– potential as an ergogenic aid. Applied physiology, nutrition, and metabolism = Physiologie appliquee, nutrition et metabolisme 33: 1284-1289.
Mohr M, Nielsen JJ, Bangsbo J (2011) Caffeine intake improves intense intermittent exercise performance and reduces muscle interstitial potassium accumulation. Journal of applied physiology 111: 1372-1379.
Doherty M, Smith PM (2005) Effects of caffeine ingestion on rating of perceived exertion during and after exercise: a meta-analysis. Scandinavian journal of medicine & science in sports 15: 69-78.
Tarnopolsky M, Cupido C (2000) Caffeine potentiates low frequency skeletal muscle force in habitual and nonhabitual caffeine consumers. Journal of applied physiology 89: 1719-1724.
Wiles JD, Bird SR, Hopkins J, Riley M (1992) Effect of caffeinated coffee on running speed, respiratory factors, blood lactate and perceived exertion during 1500-m treadmill running. Br J Sports Med 26: 116-120.
Jenkins NT, Trilk JL, Singhal A, O’Connor PJ, Cureton KJ (2008) Ergogenic â€¨effects of low doses of caffeine on cycling performance. Int J Sport Nutr Exerc Metab 18: 328-342.
Desbrow B, Biddulph C, Devlin B, Grant GD, Anoopkumar-Dukie S, et al. (2012) The effects of different doses of caffeine on endurance cycling time trial performance. Journal of sports sciences 30: 115-120.